Materials such as GaN provide improved carrier mobility and have a wider band gap than silicon. Therefore the use of GaN as a channel material in the fabrication of transistors has been found to provide transistors with a lower drain-source resistance Rdson. Also, due to the wider band gap the impact ionization is reduced causing the channel breakdown to be much higher. As a result transistors with higher voltage capability can be fabricated or the area of the transistor can be reduced for a given voltage resulting in lower capacitive losses. This allows GaN devices to be run at higher frequencies than silicon transistors of comparable power.
The problem with the use of GaN as a channel material is that to date, defect free, useful epitaxial deposition of GaN is achievable only on <111> orientation silicon substrate material, while CMOS is typically processed on <100> orientation wafers. This places practical constraints on using GaN in conjunction with CMOS processing.
The present application seeks to address this problem.